Stroke type drill stem tester

ABSTRACT

A stroke type drill stem tester has an elongated outer body connectable to the drill pipe therebelow, and an elongated inner body connectable to the drill pipe thereabove, the bodies being telescopic and defining an energizing cylinder response to the pressure of fluid in a well bore for normally holding the bodies telescopically extended. The bodies define a hydraulic delay cylinder to retard telescopic contraction of the bodies. The bodies have a valve section including a well bore fluid pressure balancing cylinder. The valve is opened upon telescopic contraction of the bodies and closed upon telescopic extension of the bodies.

United States Patent 1 1 Scott 1 STROKE TYPE DRILL STEM TESTER [75] inventor: Lyle B. Scott, South Gate, Calif.

[73] Assignee: Byron Jackson, lnc., Long Beach,

Calif.

22 Filed: Mar.l1,1974

21 Appl. No.: 449,879

[52] U.S. Cl. 166/152; 166/5; 166/150 [51] Int. Cl. E21B 47/00; E21B 49/00 [58] Field of Search 166/152, 150, 151, 133, 166/15, 264; 175/297; 73/151 [56] References Cited UNITED STATES PATENTS 3,096,823 7/1963 Crowe 166/264 X 3.280.917 10/1966 Kisling 166/152 X 3,405,773 10/1968 Sutliff et al. 175/297 3,562.807 2/1971 Slator et a1. 175/297 3,646.995 3/1972 Manes et a1. 166/152 X limbs [451 Aug. 19, 1975 Primary Examiner-David H. Brown Attorney, Agent, or Firm-John 0. Evans, Jr.

[57] ABSTRACT A stroke type drill stern tester has an elongated outer body connectable to the drill pipe therebelow, and an elongated inner body connectable to the drill pipe thereabove, the bodies being telescopic and defining an energizing cylinder response to the pressure of fluid in a well bore for normally holding the bodies telescopically extended. The bodies define a hydraulic delay cylinder to retard telescopic contraction of the bodies. The bodies have a valve section including a well bore fluid pressure balancing cylinder. The valve is opened upon telescopic contraction of the bodies and closed upon telescopic extension of the bodies.

6 Claims, 9 Drawing Figures L me PATENTEU Ant; SE75 3 900.068

STROKE TYPE DRILL STEM TESTER BACKGROUND OF THE INVENTION In the drilling and completion of wells, such as oil and gas wells, it becomes desirable to perform so-called drill stem tests. Such tests are conducted by apparatus adapted to be lowered into the well bore in a string of drill pipe to the vicinity of the earth zone to be tested. A well bore packer is set in sealing engagement with the well bore, either with the well casing or with the bore hole wall to separate the earth formation being tested from the fluid in the annular space between the drill pipe and the well bore wall above the packer. Conventionally, the apparatus includes a valve which is normally closed to shut-in the formation or earth zone being tested. When the test is to be conducted the valve is opened by manipulation of the drill pipe string to allow a quantity of fluid from the earth zone or formation to flow through the open valve into the drill pipe.

The prior art involves various tools operable in response to rotation or in response to longitudinal movement of the drill pipe string. Those tools which are responsive to longitudinal movement of the drill pipe string are generally referred to as stroke type tools, as distinguished from the rotary type drill stem testing tools.

Various problems are encountered in the running and in the use of stroke type testing tools which are caused by the pressure of the fluid in the well bore annulus above the packer. as well as by the formation pressure acting on the normally closed testing valve.

SUMMARY OF THE INVENTION The present invention involves a stroke type drill stem testing tool which beneficially utilizes the hydrostatic pressure of the annulus fluid above the packer to hold the testing valve closed and to assist in reclosing the testing valve after it has been opened. The present invention provides drill stem testing apparatus wherein in its closed condition the valve is not adversely affected by formation pressure below the packer, in that the tool incorporates balancing means for balancing the formation pressure across the testing valve, thus reducing the weight required to open the valve. The present invention also includes hydraulic delay cylinder means which retards the opening of the valve when the weight of the drill pipe is being set down until the packer is set and anchored.

More particularly, the present drill stem tester assembly has an elongated inner body connectable to the drill pipe extending to the surface, and an elongated outer body connectable to the drill pipe below the bodies. Between the bodies of the tool is an energizing cylinder having a piston area carried by the inner body and exposed to the pressure of fluid in the well bore annulus above the packer and designed to urge the inner body towards an upper position with respect to the outer body with the testing valve closed. When the valve is to be opened and the drill pipe string is lowered to move the inner body downwardly. the annulus fluid is displaced by the energizing piston from a cylinder. When the drill pipe weight is reduced annulus fluid pressure acting on the energizing piston works to return the inner body to the upper position. Accordingly, instead of employing heavy andlarge spring means to overcome the weight of the drill pipe to close the testing valve, the annular fluid pressure acting on the energizing piston serves as the means for overcoming drill pipe weight while maintaining a downward force on the packer so that the drill pipe weight need not be completely removed from the inner body in order for the valve to be closed.

In order to retard the downward movement of the inner body and transmit a force downwardly to the outer body to set and anchor a packer while the testing valve is still closed, a hydraulic delay cylinder is provided between the two bodies which contains a quantity of hydraulic fluid through which an orifice member moves as the inner body moves downwardly so that the downward force is transmitted to the outer body. During the last increment of downward movement of the inner body relative to the outer body the movement is uninhibited by the hydraulic delay cylinder.

Depending upon the pressure of the fluid in the formation being tested when the formation is shut-in by the testing valve, more or less pressure acts on the valve acting to hold the valve closed and that pressure may be very substantial and must be overcome by the weight of the drill pipe being lowered onto the inner body. In order to reduce the necessary weight so that excessive weight is not imposed on the packer, the apparatus of the invention has balancing means whereby the shut-in formation pressure acts on a piston to pressurize a quantity of internal oil. The oil pressure is applied to a piston carried by the moveable valve member and acts in a direction to open the valve, thus reducing the drill pipe weight necessary to open the valve.

In many instances it may be desireable upon removing the testing tool from the well, to bring to the top of the well a quantity of the formation fluid for further analysis. Accordingly, the present invention may have below the testing valve a reservoir fluid sampler which receives a quantity of the formation fluid.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of the form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. They will now be described in detail, for the purpose of illustrating the general principals of the invention; but it is to be understood that such detailed descriptions are not to be taken in a limiting sense.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view illustrating a string of testing tools including the stroke type drill stem tester installed in a well bore;

FIGS. 2a, 2b, 2c and 2d, together, constitute a view partly in longitudinal section as taken on the line 2-2 of FIG. I, and partly in elevation showing the drill stem tester with the valve closed, FIGS. 2b, 2c'and 2d being successive downward continuations of FIG. 2a; and

FIGS. 3a, 3b, 3c and 3d, together, constitute a view partly in longitudinal section as taken on the line 22 of FIG. 1, and partly in elevation showing the drill stem tester with the valve open, FIGS. 3b, 3c and 3d being successive downward continuations of FIG. 3a.

DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in the drawings, the drill stern tester assembly T comprises an outer elongated body I and an inner elongated body 2. At its lower end, the outer body has a connector sub 3 for connecting it in the string of testing tools extending downwardly in the well casing C, and the inner body 2 has an upper sub 4 for connecting it with a string of drill pipe S extending upwardly in the well casing. Beneath the testing tool assembly is a well packer assembly P having sealing elements 5 expansible into sealing engagement with the well casing C, and anchor elements or slips 6 adapted to be expanded into anchoring engagement with the well casing C, as is customary. Below the packer P is a typical test instrument I which communicates with the well bore below the packer P, and more particularly, communicates with the earth zone or formation F externally of the casing, through perforations 7 in the casing. The packer P is set and anchored in the casing C by the weight of the drill string S transmitted downwardly through the testing valve assembly, and separates the formation fluid in the casing below the packer from other fluid in the annulus 8 above the packer. A typical testing string may also include an unloader valve 9 between the lower end of the testing tool T and the packer P, to equalize pressure when the packer is to be released. The packer P may be made in accordance with U.S. Pat. No. 3,094,169, granted June 18, 1963, and the unloader valve may be made in accordance with U.S. Pat. No. 3,094,306, granted June 18, 1963. In any event these tools provide a flow path through which formation fluid can flow from the formation F upwardly into and through the testing tool T, and thence upwardly in the pipe string during a formation test. The instrument I may be a well known pressure and time recorder.

The purpose of the testing tool T is to provide a shutin valve assembly on which the packer P and the instrument 1 are lowered into the well bore or casing C, the packer set and anchored, and the flow of fluid from the formation selectively controlled by manipulation of the pipe string S upwardly and downwardly, that is, the weight of the pipe string S is increased or decreased to cause the inner body 2 of the testing tool T to be stroked relative to the outer body 1.

Referring to FIGS. 2a through 2d and 3a through 3d, it will be seen that the outer body 1 comprises an elongated assembly including an upper internally splined head 10 engaged with an externally splined member 11 above the inner body 2, so that the tool assembly T will rotate as a unit, for example, to effect control of the setting and anchoring of the packer P. However, the bodies 1 and 2 are relatively telescopic. Connected at 12 to the outer body head 10 is a cylindrical section 13 having a lower head 14 which is threadedly connected at 15 to a downwardly extended cylindrical section 16 of the body 1. The inner body 2 includes an elongated tubular body member 17 threadedly connected at 18 to the splined member 1 l, and extending downwardly within a suitable packing 19 in the head 14 of the outer body member 13. The annular space 20 between the body members 13 and 17 is vented at 21 and 22 to allow the transfer of fluid between the annular space 8 externally of the body 1 and the internal annular space 20.

The outer body member 16 surrounds energizing cylinder means 23, the purpose of which is to utilize the hydrostatic pressure of fluid in the well casing annulus 8 to provide a force acting upwardly on the inner body 2 and a force acting downwardly on the outer body I. This force tends to hold the bodies in a telescopically extended condition until sufficient drill string weight is imposed on the inner body 2 to overcome the hydrostatic pressure and move the inner body 2 downwardly relative to the outer body 1, as will be later described.

More particularly, the energizing cylinder means 23 comprises an inner tubular body 24, the lower portion of which extends downwardly through an external packing 25 carried by an annular cylinder head member 26 to which the outer cylinder section 16 of the energizing cylinder means is connected at 27. Between the upper head 14 and the lower head 26 is an elongated cylinder 28 which abuts at its lower end 29 with a shoulder formed on the head 26, and abuts at its upper end 30 with the upper head 14. Adjacent the upper end 30 of the cylinder 28 is a radially outwardly extended sealing flange 31 having suitable sealing rings 32 forming a seal at the upper end of the cylinder 28 within the cylinder section 16 above a port 33 in the latter which establishes communication between the well bore annulus 8 and an annular chamber 34 defined between the outer cylinder member 16 and the inner cylinder 28. At its lower end the cylinder 28 is radially ported at 35 to establish communication between the annular chamber 34 and an inner piston chamber 36 defined between the inner tubular body 24 and the cylinder 28.

The tubular body 24 and the upper inner tubular body 17 are interconnected by a split sleeve swivel 37 and a piston sleeve 38. The piston sleeve 38 is threaded at 39 to the upper sleeve 17 and has a radially outwardly projecting piston 40 provided with a ring seal 41 slideably engaging within the cylinder 28, and the split sleeve swivel 37 interconnects abutting flanges 42 and 43 on the piston sleeve 38 and the tubular body 24, respectively. The split sleeve swivel connection of the inner bodies 24 and 17 at the piston chamber 36 enables the upper portion of the tool to be separated from the lower portion of the tool at the threaded connection 27 and at the swivel 37 for cleaning and dressing of the upper portion of the tool.

Below the energizing cylinder means 23 is hydraulic delay cylinder means 44 for retarding telescopic contraction of the bodies 1 and 2 when the weight of the pipe string S is lowered on the inner body 1, so that the force is transmitted from the inner body 2 to the outer body 1, and thence to the unloader valve 9 and the packer P to close the unloader and set the packer before opening of the valve, as will be later described. This hydraulic delay cylinder means comprises an inner cylindrical body 45 connected with the tubular body 24 at 46, and an outer cylindrical body 47 connected at 48 to the previously described head 26. The outer cylindrical body 47 has a head 49 provided with a packing 50 slideably engaged with the inner cylindrical body 45. in upwardly spaced opposed relation to the head 49 is an upper cylindrical head 51 having a seal 52 with the outer cylinder body 47. At the juncture 46 between the body section 24 and the inner cylindrical body 45 is a supporting sleeve 53 having an upper shoulder 54 and a lower stop ring 55 between which is disposed an annular orifice member 56 having a number of longitudinal slots 57 at its inner periphery and a restricted orifice 58 at its upper end. About its outer periphery the orifice ring 56 has a piston ring 59 adapted to normally hold the orifice ring 56 against movement within the cylindrical body 47 and to form a seal with the outer cylinder body 47. Adjacent'the lower end of the cylindrical body 47 are a numberfoflorigitudinally extended relief grooves 60, which, as will be later described,

allow freedom of transfer of fluid in the delay chamber 61 past the orifice member 56 during the final increment of downward movement of the orifice member 56. At all other times such downward movement is inhibited by the resistance to transfer of fluid past the orifice member 56 as the inner body 2 moves downwardly relative to the outer body 1. in order to fill the delay chamber 61 with hydraulic fluid, suitable fill and bleed openings 62 and 63 are provided in the outer cylinder body 47.

Below the delay cylinder body is a valve sleeve 64 connected at 65 to the cylinder body 45 and having at its lower end a cylindrical section 66 provided with radial ports 67 and a series of axially spaced peripheral sealing elements 68 slideably and sealingly engaged within a bore 69 in a cylindrical valve body 70. When in the upper position of the inner body 2, the valve ports 67 are closed within the bore 69 of the valve body 70 as seen in FIG. 20. However, when the inner body 2 is moved downwardly as seen in FIG. 30, the valve ports 67 are open to allow formation fluid to flow upwardly through the tubular inner body assembly.

At its lower end, the cylindrical section 66 of the valve sleeve 64 may be plugged off, but in the structure shown, an elongated central tube 71 of reservoir fluid sampling means 72 is connected to the valve sleeve at 74. In either case, the cross-sectional area of the valve sleeve is exposed to the pressure of formation fluid entering the well bore from the fonnation F when the valve is closed. Accordingly, a large upward force may be applied to the inner body 1 resisting downward movement of the latter. If such large force is overcome by the drill string weight, excessive downward loading of the packer may result before the valve opens.

To obviate this problem, formation fluid pressure balancing means 75 are provided, as seen in FlG. 2c. More particularly, an outer cylindrical section 76 of the outer body 1 is connected at 77 at its upper end, to the head 49 of the delay cylinder 47 and at 78 at its lower end to an upper head '79 of the formation fluid sam pling means 72. The cylindrical section of the valve body 70 is connected at 80 to a support ring 81 and defines with the outer cylinder 76 an annulus 82. To the upper end 83 of the valve body is connected an intermediate cylinder 84 which defines with the outer cylinder 76 an upward extension of the annulus 82, the intermediate cylinder 84 also defining with the inner cylinder 64 an annulus 85. At its upper end, the intermediate cylinder 84 is engaged within a ring 86 having passage means 87 communicating with the annulus 82 and with a chamber 88 in the head 49. Formed on the inner cylinder 64 is a piston 89 having a ring seal 90 engaged in the intermediate cylinder 84 so that the annulus 85 is isolated from chamber 88 referred to above. This annulus 85 contains air, but the annulus 82 contains oil or hydraulic fluid supplied through a fill opening 91 in the outer cylinder 76 communicating with the passage means 87. The fluid in the annulus 82, the chamber 88 and the annulus 85 is confined between the piston 89 on the inner cylinder 64 and a free piston 92 in the lower portion of the annulus 82, this free piston having inner and outer side ring seals 93 and a downwardly facing elastomeric sealing cup 94 which is exposed to the pressure of formation fluid in the upper head 79 of the fluid sampler 72.

It is now apparent that the oil or fluid in the annulus 82 is pressurized by formation fluid pressure acting on the free piston 92, and the pressure of the fluid in the annulus 82 is applied to piston 89 on the inner cylinder 64 to apply a downward force on the valve body. proportional to well fluid pressure, which acts in opposition to the force derived from formation fluid pressure acting to hold the valve closed. The necessary weight of the drill string to open the valve is accordingly reduced.

The formation fluid sampler 72 includes a lower head 95 connected to the upper head 79 by an outer cylinder 96. The upper head 79 has a bore 97 slideably and sealingly engaging the upper end 98 of an inner sleeve 99 which has its lower end 100 slideably and sealingly engaging within the bore 101 of the lower head 95. When the tubular inner member 71 of the sampler 72 is in the upper position of FIG. 2d, the sleeve 99 is held in its upper position against stop elements 102 by a coiled compression spring 103 which seats in a cup 104 carried by the lower end closure 105 for the tubular member 71 and acts upwardly on the sleeve 99.

When the apparatus is operated to open the valve a shoulder 106 on the tubular member 71 engages and forces the sleeve 99 downwardly to the position of FIG. 3d allowing the annular space 107 between the sleeve 99 and the outer cylinder 96 to be filled with a sample of the formation fluid which flows into the tool through the annular space 108 between the sleeve 99 and the tubular member 71. Such a sampler is more particularly disclosed in my prior U.S. Pat. No. 3,437,138.

From the foregoing it is apparent that the present invention provides drill stem testing apparatus responsive to the stroking of the string of drill pipe to open the testing valve, without requiring the imposition of great weight on the apparatus to open the valve against shutin formation pressure and without relieving the apparatus of all of the set down weight when the valve is to be closed. Accordingly, the packer is not overly loaded by set down weight, nor is the weight in the packer relieved to an extent tending to allow the packer to shift under the influence of formation pressure.

In operation the testing tools, including the packer P, the unloader valve 9, drill stem tester T, and any suitable testing instrument I are made up at the lower end of the drill pipe string 5. Preliminarily, the annular spaces 34 and 36 of the energizing cylinder means 23 are filled with oil through the filler 33, and the testing string is lowered into the well bore to the vicinity of the formation F which is to be tested. During lowering of the test string the weight of the outer body 1 and the tools therebelow is supported on a head or shoulder 11a of the splined member 11 engaging beneath shoulder 10a of the outer spline member 10. Rotation of the pipe string S is transmitted through the splined connection between the inner and outer bodies of the testing tool, to condition the packer to be set responsive to the lowering of the drill string weight. As the drill string weight is lowered upon the inner body 1, the hydraulic delay cylinder means 44 initially transmits the downward force to the outer body 1 and thus, to the unloader valve and the packer to close and set them, respectively. Thereafter, further lowering of the drill string causes the delay piston 56 to move downwardly in the annulus 61 as the fluid therein bypasses through the restricted orifice 58. At the same time the piston 40 displaces a quantity of the oil from the annulus 36 and the annulus 34 outwardly through the opening 33 of the energizing cylinder. Continued downward movement moves the valve sleeve 66 from the open lower end of the valve body 70, as seen in FIG. 30, allowing formation fluid to flow upwardly through the inner body 2 and into the drill string. As previously indicated. the reservoir fluid sampler 72 will also be filled with a sample of formation fluid. After a desired period of time the drill string is elevated to move the valve sleeve 66 back into the valve body 70 and during this operation the pressure of fluid in the casing annulus 8 acts on the fluid in the energizing cylinder to maintain a downward force on the outer body 1. Repeated testing cylces may be resorted to, and the use of a plurality of the valve sealing elements 68 in axially spaced relation assures that suitable sealing means will remain between the valve sleeve 66 and the valve body 70 even in the case that successive seals may be washed out by fluid during successive valve openings.

1 claim:

1. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, wherein said energizing cylinder comprises an outer cylinder carried by said outer body, an inner cylinder carried by said inner body, an intermediate cylinder carried by said outer body and defining with said outer and inner cylinder an outer chamber exposed to fluid in the well bore and an inner chamber communicating with said outer chamber, said inner cylinder having a piston sealingly engaged with said intermediate cylinder and exposed to the pressure of said fluid in said inner chamber.

2. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, wherein said energizing cylinder comprises an outer cylinder carried by said outer body, an inner cylinder carried by said inner body, an

intermediate cylinder carried by said outer body and defining with said outer and inner cylinder an outer chamber exposed to fluid in the well bore and an inner chamber communicating with said outerchamber, said inner cylinder having a piston sealingly engaged with said intermediate cylinder and exposed to the pressure of said fluid in said inner chamber, wherein said inner cylinder comprises a pair of axially spaced tubular members, said piston being connected to one of said tubular members, and including split coupling means interconnecting said tubular members.

3. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid ,in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means betweensaid bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid.

4, A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively. an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid, said delay means comprising inner and outer cylindrical portions of said bodies having axially opposed heads defining a chamber, said chamber being filled with hydraulic fluid, and restricted orifice means for impeding the transfer of fluid in said chamber upon telescopic contraction of said bodies.

5. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means in cluding relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid, said delay means comprising inner and outer cylindrical portions of said bodies having axially opposed heads defining a chamber, said chamber being filled with hydraulic fluid, and restricted orifice means for impeding the transfer of fluid in said chamber upon telescopic contraction of said bodies, said valve means including a tubular valve body and a valve sleeve shiftable within said body, said valve sleeve having a plurality of axially spaced circumferential sealing elements thereon, and a port for opening said flow passage through said bodies upon telescopic contraction of said bodies.

6. A formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, and formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, wherein said balancing means comprises outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid. l 

1. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said oUter body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, wherein said energizing cylinder comprises an outer cylinder carried by said outer body, an inner cylinder carried by said inner body, an intermediate cylinder carried by said outer body and defining with said outer and inner cylinder an outer chamber exposed to fluid in the well bore and an inner chamber communicating with said outer chamber, said inner cylinder having a piston sealingly engaged with said intermediate cylinder and exposed to the pressure of said fluid in said inner chamber.
 2. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, wherein said energizing cylinder comprises an outer cylinder carried by said outer body, an inner cylinder carried by said inner body, an intermediate cylinder carried by said outer body and defining with said outer and inner cylinder an outer chamber exposed to fluid in the well bore and an inner chamber communicating with said outerchamber, said inner cylinder having a piston sealingly engaged with said intermediate cylinder and exposed to the pressure of said fluid in said inner chamber, wherein said inner cylinder comprises a pair of axially spaced tubular members, said piston being connected to one of said tubular members, and including split coupling means interconnecting said tubular members.
 3. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively, an intermediate cylInder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid.
 4. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid, said delay means comprising inner and outer cylindrical portions of said bodies having axially opposed heads defining a chamber, said chamber being filled with hydraulic fluid, and restricted orifice means for impeding the transfer of fluid in said chamber upon telescopic contraction of said bodies.
 5. A stroke type formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, energizing cylinder means between said bodies responsive to the pressure of fluid in the well bore externally of said outer body for applying a force to said bodies tending to telescopically extend said bodies, delay means between said bodies for retarding telescopic contraction of said bodies, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, including formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, said balancing means including outer and inner cylinders carried by said outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid, said delay means comprising inner and outer cylindrical portions of said bodies having axially opposed heads defining a chamber, said chamber being filled with hydraulic fluid, and restricted orifice means for impeding the transfer of fluid in said chamber upon telescopic contraction of said bodies, said valve means including a tubular valve body and a valve sleeve shiftable within said body, said valve sleeve having a plurality of axially spaced circumferential sealing elements thereon, and a port for opening said flow passage through said bodies upon telescopic contraction of said bodies.
 6. A formation tester for use in testing an earth formation penetrated by a well bore and adapted to be lowered into the well bore on a pipe string above a well bore packer which is set in the well bore by the weight of the pipe string comprising: telescopic elongated inner and outer bodies respectively having at one end means for connection with said pipe string and with said packer, said bodies defining a flow passage therethrough, and valve means including relatively longitudinally shiftable valve members carried by said bodies normally closing said flow passage when said bodies are telescopically extended and opening said flow passage when said bodies are telescopically contracted, and formation fluid balancing means between said bodies responsive to formation fluid pressure on said valve members when in said closed position for imposing a force tending to telescopically contract said bodies and to move said valve members to said open position, wherein said balancing means comprises outer and inner bodies, respectively, an intermediate cylinder, a piston carried by said inner cylinder and slideably engaged with said intermediate cylinder to define a chamber, said chamber containing air, said intermediate cylinder and said outer cylinder defining an annular space, an annular free piston in said annular space, said annular space being filled with oil, and means exposing said annular piston to the pressure of said formation fluid. 